I would get a 1/4" pin and a drill guide. you want it to be one size smaller than you think it should be. 1/32" sounds right or close. If you're worried at that diameter, you can still put on the threadlocker.

You may have a little run out on your drill press. If so, the drilled hole will be slightly larger than 3/16, which will make for a loose fit. However, can't you use a punch or thin screwdriver and open the ends of the pin slightly?

I took the plow off today, and I found out what the real problem was! It does not make any sense to me, as that part of the pin only has pressure on it when it is pulled to turn the blade.

My theory as to why it was fine when I parked it, and broke after it sat in the garage is that water got into a crack there, froze and split it apart. As it thawed out the water got deeper, and froze again... making the crack bigger until it broke. On the broken part of the pin you can see the different colors from cracks that formed at different times. I am not sure how it cracked the first time though; like I said, all pressure is forward that part of the pin.

That is strange. Did you use the blade at all? If you did and hit something hard, it could have put a jolt to the pin and cracked it. I would assume it would have had to be weak from the start though. Steel doesn't just arbitrarly break.

I did use the blade, combined I only have about an hour and a half on it; although, time does not matter when it only takes a second or two to run into a snow bank. I do not recal hiting anything though. While using it, the blade was tripping very easily, so I put the pin that prevents tripping. Since I had the pin in, more force would have been on that pin.